Pyruvate Kinase (PK) is an enzyme involved in glycolysis (the conversion of glucose into pyruvate), and is critical for the survival of the cell. PK converts phosphoenolpyruvate (PEP) and adenosine diphosphate (ADP) to pyruvate and adenosine triphosphate (ATP), respectively, which is the final step in glycolysis. PKR is one of several tissue-specific isoforms (e.g., PKR, PKL, PKM1, and PKM2) of pyruvate kinase that is present in red blood cells (RBCs). Glycolysis is the only pathway available for RBCs to maintain the production of adenosine-5′-triphosphate, or ATP, which is a form of chemical energy within cells. Accordingly, PK deficiency can result in a shortened life span for RBCs and is the most common form of non-spherocytic hemolytic anemia in humans.
PK deficiency (PKD) is a rare autosomal recessive genetic disorder that can result in severe hemolytic anemia, jaundice, and lifelong conditions associated with chronic anemia, as well as secondary complications due to inherited mutations in the pyruvate kinase enzyme within RBCs. Individuals with the PK deficiency produce PKR enzyme at only a fraction of the normal level of activity (generally <50%). There are many different possible mutant combinations, classified as either a missense mutation (causing a single amino acid change in the protein), generally resulting in some level of functional protein in the RBCs, or a non-missense mutation (any mutation other than a missense mutation), generally resulting in little functional protein in the RBCs. It is estimated that 58 percent of patients with PK deficiency have two missense mutations, 27 percent have one missense and one non-missense mutation, and 15 percent have two non-missense mutations.
There remains a need for novel compounds that activate PKR for the treatment of PK deficiency and other medical conditions that can therapeutically benefit from compounds that activate PKR.